CMOS Battery Wiring Question

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[kc27]

Does the difference between the order of the wires on the original CMOS battery connector and the order of the wiring pattern on the replacement battery connector matter?

I installed the replacement CMOS battery, but the laptop still loses the date and time.  I figure that means either the replacement battery is bad, or the difference in the order of the wires on the replacement battery connector matters. That is why I am asking about this.

 

 

 

 

 

 

 

 

• This topic was modified 3 years, 3 months ago by kc27.
• This topic was modified 3 years, 3 months ago by kc27. Reason: Add more details

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The wiring of the color coded wires does matter.

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The wires must match the color of the wire of the old battery. The red and white must be changed to match the original battery

1 user thanked author for this post.

Charlie

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I am glad you included the picture. It sounded like you were asking if the polarity of the battery matters, and yes, <span style=”text-decoration: underline;”>of course</span> it does – isn’t that obvious? But with your picture, I see the confusion – and why it is not so obvious; the red and white wires are reversed.

I am confused as to why there are even 3 wires – there are only 2 poles on a battery, the Positive and Negative poles. With the original and the red in the middle, that might be used for reverse polarity protection. But with a keyed connector (where it can only go in one that), that is not needed.

You are going to have some how determine how those wires are attached. If handy with a multimeter, you could do it that way. But I suspect you may need to cut open the blue insulating wrap to inspect the batteries to see how the wires are attached, then rewire the replacement to match. Most likely, the red is to positive, and needs to be swapped (cut, swapped, then spliced) with the white.

 

 

 

Bill (AFE7Ret)
Freedom isn't free!

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I ran into the same problem when replacing an old ThinkPad CMOS battery about 5 yrs ago. I couldn’t believe it and had to check several laptops to confirm, but I was surprised to discover not all ThinkPad models used the same CMOS battery pinout, despite using the exact same connectors.

The metal crimp-on connectors are a snap-in fit inside the plastic holder, so I cinched the plastic end in a small desk vise, used a magnifying glass and sewing needle to depress the metal latches, slid the wires+connectors out, and snapped them back in, in the proper color-coded order. The battery worked perfectly after that.

 

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Wire colour is not an indicator of correct orientation. If you change the wires around you may damage your PC / the battery, or not, per dg1261’s post.

Can you ask the battery supplier?

cheers, Paul

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You can see the battery ends are right – note the rounded edge is the side with the negative end of the battery. confirm with a meter if needs be (red should be 3V WRT black and white). I assume as you say it doesn’t fix the problem that it plugs in, so all you really need to do is ensure when you plug it in the colours of the wires still attach to the main board in the same order with the replacement battery even if the connector isn’t quite the right one.

The connectors are likely JST but the Molex one with flatter pins makes a better picture to put the detail on. I suspect you need to swap the white and red wires on the replacement I suspect. use a hat pin, small precision screwdriver, or similar pointed prove – insert, lift the tab and use the tip of the probe under the tab to hold it whilst withdrawing the wire. press the tab down with the problem to level it with the housing so the new wire locks when you push it in (note the side of the metal connector  with the “gap” goes to the tab..)

If it doesn’t work, the attempt seems likely to have killed the battery as the red wire was connected to a pin where a negative connection would normally be – I suspect the “loop” of white and black to the same terminal visible in the photo (which are likely joined) performs the function of the battery jumper on a desktop system to ensure a reset to clear any corrupt data when the battery is changed.

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Prove and problem should both be probe where they don’t make sense! I should really read the whole thing when fixing my typos..

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The order of the colored wires are the same where connected to the battery:

Red – pos side

Black and White – neg side

Therefore the connecting order to the mother board must be the same.  The red and white wires need to be switched.

The third wire is used to monitor the battery – if that function exists on the current motherboard.

HTH, Dana:))

HTH, Dana:))

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That appears to be correct.

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Go to Parts people: The Dell experts since 2002. Dell OEM Replacement Parts.
https://www.parts-people.com/
Enter Dell’s Service Tag and order the original CMOS battery for your Dell Precision M6500.

HP EliteBook 8540w laptop Windows 10 Pro (x64)

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Drcard:)) was correct, the black and white wires are tied together – see photo below. I did try parts-people.com as cmptrgy suggested, they do not have any batteries in stock. I do not have the visual acuity to do the pin swap that dg1261 and oldguy suggested.

I  did not pay attention to the order of the wires when I purchased the first replacement battery. I bought a second battery with the wires in the correct order and that solved the problem. I have purchased this type of battery in the past for other units, I must have just gotten lucky and bought compatible batteries by chance because I never checked the wire order before purchasing a CMOS battery in the past. This is the first time the order of the wires was an issue.

Thanks for all the help on this, what should have been an easy fix.

 

 

1 user thanked author for this post.

cmptrgy

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Amazing!  I have exactly the same problem on the identical machine.

Thank you to the OP and all subsequent posters.

Why would you make (and specify) two batteries with identical 3-wire connectors, but opposite polarities at the connector end???  (What could possibly go wrong?)

At least the designers were clever enough to incorporate protection against incorrect polarity — after resetting the CMOS with the correct connections, the computer seems unharmed.

— AWRon

 

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Hi I was a lot confused because I bought an old Dell e5410 laptop without a main battery and with a wired CMOS battery like your “replacement”picture. I changed the coin battery without success on maintain time/date, and I was very frustated until I tried your “original” connection and it worked. I don’t know yet if it is the final solution but maybe it would help other people with same problem.

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Hi all.

I have a very old “FIC VT-502” motherboard with                                                                                    no BIOS battery of any kind installed. And I never could get the BIOS to keep settings upon bootup. Does anyone know a trick (if possible) to wire in a much needed battery for this mobo? If there are some jumpers I can connect to or solder in if I have to?

I can’t understand how or why they could have made this board without a battery?

Maybe they forgot?? Anyway,any help would be greatly appreciated..Thanks

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Why not run an NTP client on boot? Then you don’t care what time the mobo thinks it is.

cheers, Paul

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I know I originally only asked about date and time, but doesn’t the CMOS battery preserve other BIOS settings besides date and time?

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Yes it does save the BIOS settings, but if you only use the defaults…

cheers, Paul

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It doesn’t save non-default settings?

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Paul T wrote:

Yes it does save the BIOS settings, but if you only use the defaults…

Things may be different now, but it used to be:

BIOS default settings (called CMOS) kept in permanent memory on motherboard.
User’s changes to those settings kept in temporary memory which must have power to keep memory of settings (like RAM).
Power to PC (even after Windows shut down) provides power to BIOS temporary memory.
CMOS battery supplies power to temporary memory to keep user’s changes when all power to the PC is off.
Disconnect all power to the PC and remove the CMOS battery for 1 – 5 minutes will reset the BIOS to default values because the settings in the temporary memory are gone.

So the battery is to save your changes to BIOS (such as the boot order) in case all power to the PC is stopped.

At least that used to be the way it was.

HTH, Dana:))

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